394 FLIGHT, 6 April 1951
RAIN - TRAINER . . .
freezing level in the presence of snowflakes or ice crystals
rime ice may be expected to build up on it. During flight
above freezing level through rain of the non-freezing type,
in which no ice is present, an accumulation of clear ice may
be expected on the aircraft. From this basic knowledge,
applied practically to aircraft operation, it may be possible
to forecast the probability of icing, and the type of ice to
be expected, by means of the characteristic radar echo.
Because information is required on the conditions existing
in a cloud before it starts raining, additional equipment is
carried on the DC-3 used in the investigations. For example,
the liquid content of the cloud may be measured, and two
methods are employed for this purpose. In one, a strip of
absorbent paper moves across a slot in an instrument mounted
on the port wing. The electrical resistance across the paper
varies according to the amount of water absorbed and is
continuously measured and recorded by instruments in the
main cabin. The second method involves the use of a
porous plug consisting of a number of capillary tubes which
collect the water and pass it via rubber tubing to suitable
volume-measuring apparatus.
AIRFIELD SUPER-VISION
THE radio and radar aids at present available to aircraftare all concerned with airborne movement, but a newradar aid known as A.S.M.I. (Airfield Surface Move-
ment Indicator) is designed to monitor movement on the
airfield surface. As such, its principal function is to aid the
control of all aircraft and vehicular movement on the run-
ways and perimeter tracks during fog or poor visibility.
The A.S.M.I. equipment is the logical outcome of
development work carried out by its manufacturers—
A. C. Cossor, Ltd., London, N.5—in harbour-supervision
radar, in that the technical requirements are essentially
similar, viz., high resolution (narrow beam-width, short
pulse-length), low minimum range, simplicity of display and
ease of operation for non-technical personnel. The equip-
ment operates on a wavelength of 3 cm, and with a 12-ft
wide scanner this gives a beam of but half a degree width.
A pulse-width of less than 0.1 microsecond, and a special
wide-band receiver, thus give the necessary high degree of
discrimination.
The P.P.I. display is given on a 15-in oscilloscope and, by
means of a special facility, the centre of rotation of the P.P.I.
trace can be moved anywhere over the face of the tube, so
permitting the entire screen to be used for the radar map of
the airfield. The scale of the picture presented is also adjust-
able and can, in fact, be as large as 15m to a mile.
We were able to see the performance of this new equip-
ment during a recent demonstration at London Airport.
For this purpose, the A.S.M.I, equipment had been installed
in a coach with the scanner on the roof, and was positioned
adjacent to the London Radar site. Even to unpractised
eyes the efficacy of A.S.M.I. was impressive. Certainly, the
"returns" from a large number of temporary buildings and
the extensive constructional works and equipment at the
airport were an unwanted feature but, we were assured, all
such detractions could be (and no doubt will be) "painted-
out" of the final installation. But that movement along the
runways and taxi-tracks—and along the Bath Road for that
A SAILPLANE'S "NATIONALITY"
[ concluded from page 392)
substituting a British style of lever, with cables and pulleys, for theGerman sliding bar.
(8) Complete revision of the design of the main wing and fuse-lage joints to ensure interchangeability of components, and to
permit easier rigging by a smaller ground crew.(9) Introduction of a British patent quick-release pin at all the
control de-rigging points.(10) Installation of oxygen equipment.
This redesigning involved the preparation, checking, stressinginvestigation and submission for A.R.B. approval of over 600
drawings, as well as the complete full-size "lofting" of all the con-tour lines of the aircraft. Performed by nine designers, draughts-
men and stressmen at various times over a period of about eighteenmonths, this work took about 5,000 man-hours to complete.
Flight testing for British Civil Airworthiness Requirements wascarried out by an independent body, B.G.A. Test Group No. 1,
at Redhill, and occupied about four months. Shortly after this,an Olympia Eon was flown by Mr, Charles Wingfield in the
American National Gliding Contests (at the expense of Elliotts) inorder to try it against the best the U.S.A. had to offer at that time.
The aircraft set up a new out-and-retum distance record.
The type was received with enthusiasm by the majority of soaring
A~. parked aircraft. B= control tower. C — aircraft larxjpjt,,.i .ft«»nriar site.
Radar P.P.I, map of London Airport given by tbe'A.S.M.I. equ/'jjfrnent
matter—could clearly be seen was incontrdVWtMSle, and there
can be little doubt that, by the combination of A.S.M.I.
with V.H.F. communication, the whole problem of surface-
movement control at airports large and small, particularly in
conditions of poor visibility, will be well on the way to
practical solution.
enthusiasts in this country; as proof, the makers give this analysisof entries in recent British national Contests :—
1947 1949 1950
per cent, per cent, per cent.Olympia Eon entries ... ... ... 50 52 48
All other British-design entries ... 14 20 26
Foreign-design entries ... ... 36 28 26
(There were no official contests in this country in 1948.)!Elliotts of Newbury state that the Olympia Eon's design has
been kept under constant review in consultation with official bodiesand clubs, and in the past four years this has resulted in over
twenty modifications, all aimed at "improving the breed." Com-parison of the operating limitations of the German Meise with the
1951 version of the Olympia Eon give a measure of this improve-ment. For example, the British type is authorized for an all-up
weight of 670 lb and is permitted to enter cloud, whereas the all-upweight of the Meise is 550 lb and by British standards of airworthi-
ness is not permitted to enter cloud.In the past three years, incidentally, the Olympia Eon ht-s
secured export orders to U.S.A., Iceland, Portugal, Pakistan,Australia, Canada, Denmark, Palestine, India, New Zealand,
South America, Belgium, South Africa, and Malaya.Elliotts of Newbury also produce two other glider types, the
Baby Eon and the Primary Eon, and this work, and developmentin connection with amendments for Service use, have occupu'.i
the majority of this firm's attention for the past five years.